php实现文章内容关键字增加内链

/**
*对内容中的关键词添加链接
*只处理第一次出现的关键词，对已有链接的关键不会再加链接，支持中英文
*$content:string 原字符串
*$keyword:string  关键词
*$link:string,链接
*/
function yang_keyword_link($content,$keyword,$link){
    //排除图片中的关键词
    $content = preg_replace( '|(<img[^>]*?)('.$keyword.')([^>]*?>)|U', '$1%&&&&&%$3', $content);
    $regEx = '/(?!((<.*?)|(<a.*?)))('.$keyword.')(?!(([^<>]*?)>)|([^>]*?</a>))/si';
    $url='<a href="'.$link.'">'.$keyword.'</a>';
    $content = preg_replace($regEx,$url,$content,1);
    //还原图片中的关键词
    $content=str_replace('%&&&&&%',$keyword,$content);
    return $content;
}

include_once(dirname(__file__)."/../db/DBViewSpot.php" );

class InnerLink{
    private static $spotUrlMap;
    /**
     * Generate view spots keywords link
     *
     * @param string $description
     * @param array $spotUrlMap
     * @return string
     */
    public static function genSpotLink($basePath, $description)
    {
        if(empty(InnerLink::$spotUrlMap)){
            InnerLink::$spotUrlMap = DBViewSpot::getSpotPare();
        }
        // 排除不规则数据
        if ( empty($description)) {
            return $description;
        }
        foreach (InnerLink::$spotUrlMap AS $spotUrlPair){
            $replace = "<a target='_blank' href='http://pzg412403.blog.163.com/blog/".$basePath."/".$spotUrlPair[1].".html'>".$spotUrlPair[0]."</a>";
            // 描述里面只有文字，没有图片，所以只要注意 a 链接
            $tmp1 = explode("<a",$description);
            $is_replaced=false;
            foreach ($tmp1 as $key=>$item){
                $tmp2 = explode("</a>",$item);
                if (sizeof($tmp2)>1) {
                    if (substr($tmp2[0],0,1)!="a" && substr($tmp2[0],0,1)!="A"){
                        if ($is_replaced===false) {
                            $tmp2[1] = InnerLink::str_replace_once($spotUrlPair[0],$replace,$tmp2[1],$is_replaced);
                        }
                        $tmp1[$key] = implode("</a>",$tmp2);
                    }
                }else {
                    if (is_string($item) && $is_replaced===false) {
                        $tmp1[$key] = InnerLink::str_replace_once($spotUrlPair[0],$replace,$item,$is_replaced);
                    }
                }
            }
            $description = implode("<a",$tmp1);
        }
        return $description;
    }
    /**
     * replace key word for one time
     *
     * @param string $needle
     * @param string $replace
     * @param string $haystack
     * @param bool $is_replaced
     * @return string
     */
    private static function str_replace_once($needle, $replace, $haystack,&$is_replaced) {
        $pos = strpos($haystack, $needle);
        if ($pos === false) {
            return $haystack;
        }
        $is_replaced=true;
        return substr_replace($haystack, $replace, $pos, strlen($needle));
    }
}